The present invention relates to lift boats or jack-up boats that feature a hull having a plurality of legs, each leg having an associated jacking mechanism that enables the hull to be elevated or lowered relative to the legs and wherein each leg has a load bearing pad that engages the seabed during use. More particularly, the present invention relates to an improved lift boat having an improved leg configuration that contributes buoyance by providing a specially shaped and watertight leg that has one or more racks that engage pinion gear(s) of a drive or jacking unit.
Lift boats are well known in the art. These devices are also referred to as jack up barges or jack up boats. Such vessels include a floating hull that allows the vessel to travel on a body of water. When the vessel reaches a selected locale, jacking units lower the legs and then elevate the barge or hull above the water surface so that the hull is not affected by substantial wave action.
Patents have issued for lift boats or jack up vessels. Possibly relevant examples (each incorporated herein by reference) can be found in the following table.
U.S.Pat. No.TitleIssue Date2,308,743BargeSep. 16, 19393,183,676Mobile Sea PlatformOct. 20, 19603,290,007Jack Arrangement For AJun. 28, 1965Platform Structure3,367,119Flotation Device for OffshoreJan. 20, 1966Platform Assembly3,606,251Leg Supported Offshore StructureNov. 14, 1969With Jacking Apparatus3,750,210Apparatus For The ConstructionAug. 7, 1973Of Bridges3,945,450Apparatus and Method ForMar. 23, 1976Rendering An Offshore DrillingPlatform Mobile3,967,457Self-elevating Offshore Drilling Unit LegsJul. 6, 19764,417,664Method and Apparatus ForNov. 29, 1983Mounting Lift Crane On Offshore Structures4,456,404Method and Apparatus ForJun. 26, 1984Positioning A Working Barge AboveA Sea Surface4,482,272Load Transfer And MonitoringNov. 13, 1984System For Use With Jackup Barges4,505,616Self-locking Chock SystemMar. 19, 1985For A Jack-up Rig Unit4,589,799Device For Locking Platform OfMay 20, 1986Offshore Structure4,627,768Locking Device For Oil PlatformsDec. 9, 19864,678,165Mode Of Construction Of LiftingJul. 7, 1987Mechanisms For Jack-up Platform AndLifting Mechanism For a Jack-up Platform4,722,640Slant Leg Offshore PlatformFeb. 2, 1988And Method Of Operating Same4,813,814Leg-holding Device For OffshoreMar. 21, 1989Platform5,139,366Offshore Jackup Rig LockingAug. 18, 1992Apparatus And Method5,580,189Jack-up Rig CraneDec. 3, 19965,797,703Elevating Unit For Use WithAug. 25, 1998Jack-up Rig
Some of these patented rigs/vessels employ an open truss or lattice type leg. For example, see U.S. Pat. No. 3,183,676 issued to R. G. Letourneau which shows an open truss or lattice type leg structure for a jack-up or lift boat.